In Vitro Comparison of Porcelain Fused to Metal Crown Retention after Endodontic Access and Subsequent Restoration: Composite,Amalgam, Amalgam with Composite Veneer,and Fiber Post with Composite

IntroductionThe aim of this study was to evaluate the effect of different access opening restorative materials on crown retention.MethodsThirty-eight extracted molars were mounted in resin and prepared for porcelain fused to metal (PFM) crowns. The crowns were fabricated and cemented with zinc phosphate, and the force to displace it was measured with a tensile-testing machine before and after endodontic access preparations. The endodontic access area, crown preparation axial wall, and preparation surface area were measured for comparison. The crowns were then recemented, and access openings were restored with either amalgam or composite before displacement force was remeasured. The restorative material was removed from each access opening; access area was measured and restored again (amalgam with composite or fiber post with composite) for displacement force to be remeasured. Paired t test was used to compare the means of displacement between groups. One-way analysis of variance was used to compare the mean outcome measure within the groups.ResultsStatistical analyses showed retention after unfilled access was significantly lower than intact crowns. Amalgam, composite, amalgam + composite, and fiber post + composite increased retention beyond the original value. There was no statistical difference among the different restorative protocols. Qualitative results indicate that the restorative material remains in the crown after displacement regardless of the material used to restore the access.ConclusionsThe results from this study suggest that an endodontic access cavity decreases retention of a PFM crown. However, subsequent restoration with amalgam, composite, amalgam + composite, or post + composite may increase the original retention of the crown.     

Resistance to fracture of two all-ceramic crown materials following endodontic access

STATEMENT OF PROBLEM: There is currently no protocol for managing endodontic access openings for all-ceramic crowns. A direct restorative material is generally used to repair the access opening, rendering a repaired crown as the definitive restoration. This endodontic procedure, however, may weaken the restoration or initiate microcracks that may propagate, resulting in premature failure of the restoration. PURPOSE: The purpose of this in vitro study was to evaluate how an endodontic access opening prepared through an all-ceramic crown altered the structural integrity of the ceramic, and the effect of a repair of this access on the load to failure of an all-ceramic crown. MATERIAL AND METHODS: Twenty-four alumina (Procera) and 24 zirconia (Procera) crowns were fabricated and cemented (Rely X Luting Plus Cement) onto duplicate epoxy resin dies. Twelve crowns of each were accessed to simulate root canal treatment therapy. Surface defects of all accessed specimens were evaluated with an environmental scanning electron microscope. The specimens were repaired with a porcelain repair system (standard adhesive resin/composite resin protocol) and were loaded to failure in a universal testing machine. Observations made visually and microscopically noted veneer delamination from the core, core fracture, shear within the veneer porcelain, or a combination thereof. A Kruskal-Wallis test was used to determine if a significant difference (alpha=.05) in load to failure existed between the 4 groups, and a Mann-Whitney test with a Bonferroni correction (P<.0125) was used for multiple comparisons. A Weibull analysis was also used to estimate the Weibull modulus and characteristic failure for each group. RESULTS: All specimens exhibited edge chipping around the access openings. Some displayed larger chips within the veneering porcelain, and 4 zirconia crowns showed radial crack formation. There was a significant difference in load to failure among all groups with the exception of the alumina intact and repaired specimens (P=.695). The alumina crowns generally showed fracture of the coping with the veneering porcelain still bonded to the core, whereas the zirconia copings tended not to fracture but experienced veneering porcelain delamination. CONCLUSION: Endodontic access through all-ceramic crowns resulted in a significant loss of strength in the zirconia specimens but not in the alumina specimens.     

The effect of endodontic access cavity preparation and subsequent restorative procedures on molar crown retention

Preparation of an endodontic access cavity through a full crown may affect its retention. This study was undertaken to investigate the effects on molar crown retention of endodontic access cavities and their subsequent restoration. Thirty human molars were mounted in resin, crown preparations were cut and their surface areas were determined. Vented metal copings were cemented with zinc phosphate and the forces required to displace each coping were measured using a tensile-testing machine. The copings were recemented, access cavities were cut and their surface areas determined prior to the displacement forces being re-measured. The copings were recemented, assigned to two groups, and the access cavities were restored - Group 1 with amalgam; Group 2 with glass ionomer (GIC). Displacement forces were re-measured and the copings were recemented. The occlusal margins of the access cavities were ***bevelled and restored again prior to displacement forces being re-measured. Mean displacement forces were -Group 1: Original (kg force), 37.86 ± 3.97; After access cavity, 29.28 ± 3.22; Amalgam, 50.21 ± 4.71; Amalgam + bevel, 46.45 ± 6.21. Group 2: Original, 42.77 ± 4.49; After access cavity, 39.25 ± 5.91; GIC, 48.11 ± 3.55; GIC + bevel, 39.63 ± 5.31. Statistical analyses with paired t tests showed that retentive values with access cavities were significantly lower than with intact crowns. Amalgam or GIC restorations increased retention beyond original values, significantly with amalgam. Bevelled occlusal margins decreased retention of crowns with restored access cavities but this was not significantly different from the original values. A significant relationship existed between total surface areas of the crown preparations, areas of the occlusal tables, and retentive values for crowns without access cavities. The access cavity area, as a proportion of the total area of the preparation, was related to the decrease in retention.     

Factors Associated with the Need for a Primary Endodontic Treatment after Single-Unit Crown Cementation: A Retrospective Case-Control Study

IntroductionThis case-control study aimed to identify factors associated with an increased risk for endodontic treatment after single-unit crown cementation and to describe the timeline of such events.MethodsAfter evaluating the electronic records of all single-unit crowns placed on nonendodontically treated teeth between 1999 and 2019 and excluding teeth with preexisting questionable or confirmed endodontic disease, “cases” were identified as teeth requiring primary endodontic treatment after crown cementation. This was not examined in the current study because the cases and controls were matched by tooth type.ResultsOverall, 69 teeth without any suspected or confirmed past endodontic disease required an endodontic intervention after crown cementation. The mean number ± standard deviation of restorations in a tooth before crown cementation was significantly higher among the cases than the matched controls (2.16 ± 0.99 vs 0.78 ± 0.78, P < .05). Teeth with ≥2 and ≥3 previous restorations had an almost 4 (odds ratio = 3.81; 95% confidence interval, 1.56–9.29; P < .05) and almost 6 (odds ratio = 5.97; 95% confidence interval, 1.230–28.95; P < .05) times higher risk, respectively, for endodontic treatment after crown cementation compared with teeth with ≤1 restoration present before crown cementation. The majority (65%, n = 45) of teeth in the cases group required endodontic treatment during the first 3 years after crown cementation.ConclusionsThe presence of multiple restorations at the time of crown cementation was identified as a significant predictive factor for the need for endodontic treatment after crown cementation in teeth with no preexisting questionable or confirmed endodontic disease. Therefore, clinicians should be aware and inform patients about the increased risk of primary endodontic treatment in teeth with a history of more than 1 restoration, especially during the first 3 years after permanent crown cementation.     

Fracture strength of amalgam crowns with repaired endodontic access

Endodontic therapy is accessed occlusally in posterior teeth, many of which have large, pre-existing amalgam restorations. These teeth are also commonly restored with an occlusal amalgam to repair the access opening. This study determined the fracture resistance of complex amalgam restorations that have repaired endodontic access compared with original, unrepaired, complex amalgams on endodontically-treated teeth. Two groups of 30 molars were used in the study. The first group was decoronated and received an endodontic access preparation. These teeth were restored using chamber retention and four TMS pins. The second group was decoronated and restored using pin retention. Later, they received an endodontic access through the restoration. The access was then repaired with amalgam. The samples were loaded in an Instron Universal Testing Machine until failure. The Group 1 samples failed at a mean force of 2297.5 N. The mean failure load for the samples in Group 2 was 1586.1 N. Student's t-test found this difference to be statistically significant. Endodontic access through an amalgam crown significantly compromises the fracture strength of the original restoration.     

A 5-year retrospective study of survival of zirconia single crowns fitted in a private clinical setting

ObjectivesThe aim of this report was to evaluate the 5-year clinical performance and survival of zirconia (NobelProcera?) single crowns.MethodsAll patients treated with porcelain-veneered zirconia single crowns in a private practice during the period October 2004 to November 2005 were included. The records were scrutinized for clinical data. Information was available for 162 patients and 205 crowns.ResultsMost crowns (78%) were placed on premolars and molars. Out of the 143 crowns that were followed for 5 years, 126 (88%) did not have any complications. Of those with complications, the most common were: extraction of abutment tooth (7; 3%), loss of retention (15; 7%), need of endodontic treatment (9; 4%) and porcelain veneer fracture (6; 3%). No zirconia cores fractured. In total 19 restorations (9%) were recorded as failures: abutment tooth extraction (7), remake of crown due to lost retention (6), veneer fracture (4), persistent pain (1) and caries (1). The 5-year cumulative survival rate (CSR) was 88.8%.ConclusionsAccording to the present 5-year results zirconia crowns (NobelProcera?) are a promising prosthodontic alternative also in the premolar and molar regions. Out of the 143 crowns followed for 5 years, 126 (88%) did not have any complications. However, 9% of the restorations were judged as failures. Further studies are necessary to evaluate the long-term success.     

10-year practice-based evaluation of ceramic and direct composite veneers

ObjectivesThis 10-year practice-based study aimed to compare survival and success of direct resin composite and ceramic veneers placed in a private dental practice, between January 2008 and March 2014.MethodsData were retrieved from a clinical practice’s records and were anonymized typed into electronic files. All veneer information was recorded, including previous restorations, repairs or failures, materials used, dates, patient, and age.ResultsWe analyzed 1459 veneer restorations, of which 1043 (71.5%) were direct composite, and 416 (28.5%) were ceramic, placed in 341 patients. The mean patients’ age was 47.8 years, and the mean number of restorations per patient was 4.3 restorations. During all follow-up, 957 (65.6%) veneers were successful without any repair, 252 (17.3%) were repaired and still in place, and 250 (17.1%) had a failure that resulted in replacement. Replacements were usually carried out with the same material placed at first. Considering success analysis, annual failure rates (AFR) for veneers in 5 and 10 years were 9.1% and 10% for direct composite and 2.9% and 2.8% for ceramic, respectively. Survival analysis showed AFR of 3.9% and 4.1% for composite and 1.4% and 1.2% for ceramic at the same periods. Cox regression was made for both success and survival outcomes. Composite veneers presented a higher risk of failure than ceramic veneers with higher hazard ratios for survival (HR) [HR 4.00 (2.74–5.83)] and success [HR 5.16 (2.65–10.04)].SignificanceCeramic veneers had superior longevity than direct composite veneers in both success and survival analysis.     

Influence of previous restoration of the tooth on prognosis of crowns with dowels

Due to extensive loss of tooth substance the restoration of endodontically treated tooth requires intracanal dowels to give an efficient strength for the crown. The aim of our study was to investigate whether the previous type of restoration of the tooth, i.e. composite restoration with screw post versus one-piece dowel crown, has an effect on the prognosis of crowns with dowels. The material consisted of 111 single crowns and as a previous restoration there were 83 composite restorations with screw posts and 28 one-piece dowel crowns. The mean follow-up time was 78 months (range 6--163 months). The cumulative survival was 87% for one-piece dowel crowns and 84% for composite resins with screw posts. There were six root fractures, four losses of cement retention and one tooth extraction due to caries in crowns with previous composite resin with screw posts. In one-piece dowel crowns as a previous restoration there were two root fractures and one tooth extraction for periodontal reasons. In conclusion, it seems that the previous restoration has no marked effect on the prognosis of crowns with dowels when studying a composite resin restoration with screw post and a one-piece dowel crown.     

The Incidence of Root Canal Therapy after Full-Coverage Restorations: A 10-Year Retrospective Study

IntroductionThe process of restoring a tooth with a crown leaves many opportunities for pulpal irritation. The objective of this study was to identify and analyze the factors that contribute to the incidence of nonsurgical root canal therapy (NS-RCT) after the delivery of single-unit full-coverage restorations.MethodsInsurance claims from 88,409 crown placements in the Delta Dental of Wisconsin insurance database were analyzed from the years 2008–2017. The Cox regression model was used to analyze the effect of the predictor variables on the survival of the tooth. Untoward events were defined as NS-RCT, tooth extraction, retreatment of root canal, or apicoectomy as defined by the Code on Dental Procedures and Nomenclature.ResultsOf 88,409 crowns placed, 8.97% were complete metal, 41.40% were all ceramic, and 49.64% were porcelain fused to metal (PFM). The probability of survival of all teeth with crowns placed was 90.41% after 9 years. NS-RCT was the most common untoward event. PFM crowns exhibited a higher rate of untoward events than complete metal crowns and a lower rate than all-ceramic crowns. Crowns placed on individuals 50 years of age and younger had higher rates of untoward events than those placed on individuals ages 51 years and older.ConclusionsThe risk of endodontic treatment after the placement of crowns is low. This risk increases with the placement of all-ceramic or PFM crowns and as the age of the patient decreases.     

Incidence of endodontic therapy after complete or partial coverage glass-ceramic restorations with a follow-up time of over 30 years: A prospective clinical study

Statement of problemLong-term clinical data are lacking on the comparison of the incidence of endodontic therapy in adhesively luted complete and partial coverage glass-ceramic restorations, as well as on the effect of technique and clinical variables.PurposeThe purpose of this prospective clinical study was to assess the long-term incidence of teeth requiring endodontic therapy after receiving either complete or partial coverage glass-ceramic restorations.Material and methodsParticipants requiring single anterior complete, posterior complete, or posterior partial (inlay or onlay) coverage restoration, or a combination of these on a vital tooth were recruited from a clinical private practice. Only the participants who chose glass-ceramic partial and complete coverage restorations without the need of endodontic therapy were included in the study. The overall clinical performance of these glass-ceramic restorations was assessed by clinical factors determined at recall. The effect of various clinical parameters (type of restoration, dental arch, tooth position in the dental arch, age and sex of participant, and ceramic thickness) was evaluated by using Kaplan–Meier survival curves to account for attrition bias and other reasons for failure. The statistical significance of differences between parameters was determined by using the log rank test (α=.05).ResultsA total of 1800 participants requiring 4511 glass-ceramic anterior and posterior restorations were evaluated. The mean age of the participants at the time of restoration placement was 62 (range 20 to 99 years, 710 men and 1090 women). Of 4511 restorations, 1476 were anterior complete coverage, 2119 posterior complete coverage, and 916 posterior partial coverage. Endodontic therapy after restoration placement was needed for 76 restorations (10 anterior complete, 50 posterior complete, and 16 posterior partial). The total time at risk was 50 436 years providing an estimated need for endodontic therapy risk of 0.15% per year. The estimated 35-year cumulative survival was 97.36%. The majority of endodontic treatments (67%, 52/76) occurred in the first 5 years.The estimated cumulative survival of anterior complete coverage, posterior complete coverage, posterior partial inlay, and posterior partial onlay restorations was 98.89% (n=1476, 10 endodontic treatments), 96.38% (n=2119, 50 endodontic treatments), 96.78% (n=553, 11 endodontic treatments), and 98.53% (n=363, 5 endodontic treatments), respectively. Statistically significant differences occurred between anterior complete coverage, posterior complete coverage, and posterior partial coverage inlay restorations, with a higher incidence in posterior complete coverage and posterior partial inlay restorations (P<.05). First molars had the highest rate of endodontic therapy after restoration in both arches. Age and restoration thickness were significant factors, recording statistically higher number of endodontic treatments in participants >52 years and restorations with all surfaces ≥1 mm (P<.05). Other clinical variables, dental arch and sex of the participants, were not significantly related to endodontic treatments (P>.05).ConclusionsThe clinical performance of 4511 units over 30 years in service was excellent, with the estimated cumulative survival of 97.36%. Posterior complete coverage and posterior partial inlay restorations had a significantly higher need for endodontic therapy than anterior complete coverage restorations. Their overall clinical performance relative to endodontic treatment was excellent with a cumulative survival of 96.38% and 96.78% over 30 years. There was no difference in the endodontic treatment rate between posterior complete and partial coverage restorations. Thickness of the restoration affected the endodontic treatment rate, with ≥1 mm resulting in higher incidence. The age of the participants influenced the endodontic treatment rate, with higher incidence in the >52-year age group. Other confounding clinical variables did not have a significant effect on the endodontic treatment rate.     

Cumulative effects of successive restorative procedures on anterior crown flexure: intact versus veneered incisors.

OBJECTIVE: When successive restorative procedures (e.g., porcelain veneers, interdental resin composite restorations, and endodontic treatment) are carried out on the same tooth, significant effects on crown flexure can be expected. METHOD AND MATERIALS: Dentin-bonded porcelain veneers (experimental group) were assessed in vitro using functional and cyclic thermal loads. They were compared to natural teeth (control group) with respect to 2 parameters: coronal flexure (investigated using experimental strain gauges) and morphology of the tooth-restoration interface (scanning electron microscopic evaluation). For both veneered and natural teeth, crown deformation was recorded at 5 sequential experimental steps: intact tooth (baseline), Class III cavities, Class III resin composite restorations, endodontic treatment, and endodontic restoration (without posts). RESULTS: No significant differences in crown flexure were found between natural and veneered incisors when compared across experimental steps. The main effect for experimental steps was highly significant. When averaged across all specimens (natural and veneered teeth), the endodontic treatment step resulted in the highest crown flexure (1.55x the baseline value). The unrestored Class III cavities and the endodontic restoration were next highest (1.30x and 1.28x the baseline value, respectively). The lowest crown flexures were found after restoration of the Class III cavities (1.13x the baseline value). No measurable microleakage or gaps were detected at the ceramic-resin, resin-enamel, or resin-dentin interfaces (Optibond FL, Kerr). CONCLUSION: Each subsequent reduction in tooth structure resulted in a substantial increase in crown flexibility, even after restoration. Endodontic procedures were responsible for most of the loss in crown stiffness. Extensive proximal cutting and restorations seemed to minimally affect crown flexure. Porcelain veneers showed perfect biomimetic behavior, because cumulated restoration procedures had the same effect on natural and veneered incisors.     

Risk factors for failure of glass fiber-reinforced composite post restorations: a prospective observational clinical study

Glass fiber-reinforced endodontic posts are considered to have favorable mechanical properties for the reconstruction of endodontically treated teeth. The aim of the present investigation was to evaluate the survival of two tapered and one parallel-sided glass fiber-reinforced endodontic post systems in teeth with different stages of hard tissue loss and to identify risk factors for restoration failure. One-hundred and forty-nine glass fiber-reinforced endodontic posts in 122 patients were followed-up for 5-56 months [mean +/- standard deviation (SD): 39 +/- 11 months]. Glass fiber-reinforced endodontic posts were adhesively luted and the core was built with a composite resin. Cox proportional hazards models were used to evaluate the association of clinical variables and failure rate. Higher failure rates were found for restorations of anterior teeth compared with posterior teeth [Hazard-Ratios (HR): 3.1; 95% confidence interval (CI): 1.3-7.4], for restorations in teeth with no proximal contacts compared with at least one proximal contact (HR: 3.0; 95% CI: 1.0-9.0), and for teeth restored with single crowns compared with fixed bridges (HR: 4.3; 95% CI: 1.1-16.2). Tooth type, type of final restoration and the presence of adjacent teeth were found to be significant predictors of failure rates in endodontically treated teeth restored with glass fiber-reinforced endodontic posts.     

Five-year clinical performance of posterior resin composite restorations placed by dental students

OBJECTIVES: To investigate the survival over a five-year period of posterior resin composite restorations placed by students. METHODS: Class I and II resin composite restorations placed by second-fourth year dental students were evaluated. Patients attended the dental school every 6 months for a regular check-up during which all restorations were checked on their clinical acceptability. In case of replacement or repair of a restoration, this was registered in the patient's record. From each record the survival time and reasons for failure of resin composite restorations were gathered. RESULTS: Seven-hundred three posterior resin composite restorations in 382 patients (49% female and 51% male, age 22-78) were evaluated. At 5 years 560 of the 703 restorations were still considered to be "clinically acceptable". Forty-nine restorations were considered as "functionally present", of which 44 were restored with a crown and four had received a new restoration adjacent to the existing restoration without its removal. Ninety-four restorations had failed. The main reasons for failure were restoration fracture, caries, endodontic treatment, defective margin and lack of proximal contact. The survival rate of the restorations was 87% at 5 years, resulting in an annual failure rate of 2.8%. CONCLUSIONS: Dental students are able to place resin composite restorations in posterior teeth with an acceptable mean annual failure rate.     

Longevity of posterior resin composite restorations in permanent teeth in Public Dental Health Service: A prospective 8 years follow up

ObjectivesTo investigate in a prospective follow up the longevity of posterior resin composites (RC) placed in permanent teeth of children and adolescents attending Public Dental Health Service.MethodsAll posterior RC placed, in the PDHS clinics in the cities of Copenhagen and Frederiksberg in Denmark between November 1998 and December 2002, in permanent teeth of children and adolescents up to 18 years, were evaluated in an up to 8 years follow up. The endpoint of each restoration was defined, when repair or replacement was performed. Survival analyses were performed between subgroups with Kaplan–Meier analysis. The individual contribution of different cofactors to predict the outcome was performed with Cox regression analysis.ResultsTotally 2881 children with a mean age of 13.7 years (5–18) received 4355 RC restorations placed by 115 dentists. Eighty percent were placed in molars and 49% were Class I. Two percent of restorations with base material and 1% of the restorations without base material showed postoperative sensitivity (n.s.). Replacements were made in 406 and repairs in 125 restorations. Kaplan–Meier analysis showed a cumulative survival at 8 years of 84.3%, resulting in an annual failure rate of 2%. Lower patient age, more than one restoration per patient, placement of a base material and placement of RC: in molars, in cavities with high number of surfaces, in lower jaw teeth, showed all significant higher failure rates. Five variables had significant importance for the end point, replacement/repair of the resin composite restorations: age of patient, age of operator, jaw, tooth type and cavity size.SignificancePosterior RC restorations placed in children and adolescents in Public Dental Health clinics showed an acceptable durability with annual failure rates comparable with those of randomized controlled RC studies in adults.     

Clinical survival and performance of premolars restored with direct or indirect cusp-replacing resin composite restorations with a mean follow-up of 14 years

ObjectivesThe objective is to evaluate the long-term clinical survival and performance of direct and indirect resin composite restorations replacing cusps in vital upper premolars.MethodsBetween 2001 and 2007, 176 upper premolars in 157 patients were restored with 92 direct and 84 indirect resin composite restorations as part of an RCT. Inclusion criteria were fracture of the buccal or palatal cusp of vital upper premolars along with a class II cavity or restoration in the same tooth.ResultsForty patients having 23 direct and 22 indirect composite restorations respectively, were lost to follow-up (25.6%). The cumulative Kaplan-Meier survival rates were 63.6% (mean observation time: 15.3 years, SE 5.6%) with an AFR of 2.4% for direct restorations and 54.5% (mean observation time: 13.9 years, SE: 6.4%) with an AFR of 3.3% for indirect restorations. The Cox regression analysis revealed a statistically significant influence of the patient’s age at placement on the survival of the restoration (HR 1.036, p = 0.024), the variables gender, type of upper premolar, type of restoration, and which cusp involved in the restoration had no statistically significant influence. Direct composite restorations failed predominantly due to tooth fracture, indirect restorations primarily by adhesive failure (p < 0.05).SignificanceThere was no statistically significant difference in survival rates between direct and indirect composite cusp-replacing restorations. Both direct and indirect resin composite cusp-replacing restorations are suitable options to restore compromised premolars. The longer treatment time and higher costs for the indirect restoration argue in favor of the direct technique.     

The effect of endodontic access cavity preparation and subsequent restorative procedures on incisor crown retention

Endodontic treatment often will require access through existing crowns. This study was undertaken to determine whether endodontic access cavity preparation affected the retention of crowns in anterior teeth and then to determine whether this retention can be regained by amalgam or post-retained amalgam restorations. Twenty extracted human incisors were mounted in acrylic blocks and prepared for crowns. Metal copings were fabricated and cemented with zinc phosphate cement and the forces required to displace the copings after various procedures were measured with a tensile testing machine. Retention values for all stages were compared with the initial retentive value for each coping without an access cavity which was set at 100 per cent. Group one specimens had the following means: copings with access cavity, 85.64 ± 28.65 per cent of the initial values; amalgam flush with lingual dentine, 95.81 ± 36.2 per cent; amalgam flush with coping, 114.89 ± 34.5 per cent. Group two means were: copings with access cavity, 89.95 ± 21.42 per cent; posts and amalgam, 177.37 ± 77.5 percent. Statistical analysis with the two sample f test showed that retention with post-retained amalgam restorations showed significantly higher values when compared with access cavities without restorations (p<0.05). Retention values for post-retained restorations were significantly different from those just using amalgam. This study demonstrated that endodontic access cavities reduced the retention of the crowns, and subsequent restoration with amalgam or a post can regain the retention. Post-retained restorations showed the highest retention when compared with the amalgam restorations, but the high standard deviation in the post group indicates that the amount of retention to be gained may be clinically unpredictable.     

Influence of minimally invasive endodontic access cavities and bonding status of resin composites on the mechanical property of endodontically-treated teeth: A finite element study

ObjectiveTo study the mechanical behavior of endodontically-treated teeth with minimally invasive endodontic access cavities and resin composite restorations under different bonding conditions using finite element analysis (FEA).MethodsFour Class-II endodontic access cavities including the mesio-occlusal minimally-invasive (MO-MIE), mesio-occlusal conventional (MO-CONV), disto-occlusal minimally-invasive (DO-MIE), and disto-occlusal conventional (DO-CONV) cavities were prepared in 3D-printed maxillary first molars. Each tooth was subjected to root canal preparation and scanned using micro-CT to provide a 3D structural model which was virtually restored with resin composite. An intact 3D-printed molar was used as control. FEA was conducted under a 250-N vertical load. Three different interfacial bonding conditions between dentin/enamel and resin composite were considered, i.e. fully bonded, partially debonded, and fully debonded. The maximum principal stress of dentin and the normal tensile stress at the interfaces were recorded. The risk factor of failure for each component was then calculated.ResultsIn the fully-bonded tooth, the dentin-composite interface showed significantly higher stress and a higher risk factor than dentin, indicating that debonding at the dentin-composite interface would occur prior to dentin fracture. With the dentin-composite interface debonded, the enamel-composite interface exhibited higher stress and a higher risk factor than dentin, indicating that debonding at the enamel-composite interface would occur next, also prior to dentin fracture. With the resin composite fully debonded from the tooth, stress in dentin increased significantly. Irrespective of the bonding status, the CONV groups exhibited higher median stresses in dentin than the MIE groups.SignificanceWithin the limitation of this study, it was shown that debonding of the resin composite restoration increased the stress in dentin and hence the risk of dentin fracture in endodontically-restored teeth. Minimally-invasive access cavities could better safeguard the fracture resistance of interproximally-restored teeth compared to conventional ones.     

Outcome of Endodontic Treatment through Existing Full Coverage Restorations: An Endodontic Practice Case Series

IntroductionThis case series assessed the outcome of nonsurgical endodontic treatment completed through retained full coverage restorations (FCRs) in a board-certified endodontist private practice. The number of cases completed by the first author was 153.MethodsAll cases were performed following a standardized protocol for treatment and restoration depending on the type of FCR. Number of cases that showed up for 2- to 4-year follow-up was 127, with 83% recall rate. The age range of patients was 33–95 years, with mean age of 54.734 years. The mean recall time was 2.448 years. FCRs and their distribution were as follows: 4 anterior teeth, 14 premolars, and 109 molars. There were 103 nonsurgical root canal treatments and 24 retreatments. Patients who presented for recall had 74 porcelain fused to metal crowns, 17 zirconia crowns, 15 abutments of porcelain fused to metal bridges, 14 lithium disilicate crowns, 5 gold crowns, 1 full metal crown, and 1 gold onlay.ResultsThere were no endodontically related failures. Six cases failed; 3 were due to vertical root fractures, 1 was due to horizontal root fracture, and 2 were due to extensive recurrent caries causing restorative failure. The percentage of healed cases following the American Association of Endodontists outcome criteria adopted in 2004 with intact retained FCR was 95.3%.ConclusionsThe results suggest predictable favorable outcomes for nonsurgical endodontic treatment through FCR following the proposed protocol for diagnosis, treatment, and restoration.     

Monomer release from direct and indirect adhesive restorations: A comparative in vitro study

ObjectivesIndirect dental restorations produced by computer-aided design and computer-aided manufacturing (CAD/CAM) are relatively new in daily dental practice. The aim of the present study was to compare the monomer release between direct composite restorations and indirect CAD/CAM produced restorations (composite, ceramic and hybrid).MethodsIdentical crown restorations were prepared from three indirect materials (Cerasmart, Vitablocs Mark II and Vita Enamic) and one composite material (Clearfil AP-X). For each restoration, eight crown restorations were luted onto tooth samples and immersed into 2.5 mL of an aqueous extraction solvent. Additionally, three nonluted crowns of each restoration type were also immersed in the extraction solvent, and served as controls. Every week, the extraction solvent was collected and refreshed, during a period of 8 weeks. The released monomers were quantified using ultra-performance liquid chromatography-tandem mass spectrometry.ResultsIndirect restorations release significantly lower quantities of residual monomers than direct restorations, and the monomers released by the luted indirect restorations are mainly derived from the composite material used for cementation. The quantity of monomers released by direct restorations greatly depended on the time of light polymerization.SignificanceIn terms of monomer release, indirect restorations are a good alternative to direct restorations to limit patient exposure to residual monomers. It is important to ideally design the fit of indirect restoration so that the cement layer is as thin as possible and the monomer release from this cement layer remains as low as possible.